Depending on the style of the shoe and the type of suede, they should be appropriate where (e.g.) a brown wingtip oxford or nice loafer would be considered appropriate. I would consider them more an autumn shoe, but I wouldn't be too picky about it either. j.
^^^I always thought of suede as a fall/winter shoe until I joined SF. I still won't wear dark colored suede in s/s, but I've seen great examples here on SF of suede in lighter colors worn with s/s attire.